This invention relates to an improved iron-based casting alloy having improved combinations of toughness, abrasion resistance and corrosion resistance, and the invention also relates to a process for making the alloy.
There are many applications for which it is desirable to have iron-based alloys that are castable and have improved combinations of toughness, abrasion resistance and corrosion resistance. For example, the paper making industry casts refiner plate alloys which can advantageously increase production at faster speeds. However, at these faster speeds, the cast refiner plates wear faster and are more susceptible to brittle fracture.
Cast alloys of iron, chromium, vanadium, niobium, and tungsten have previously been studied by A. Sawamoto et al. as set forth in the Transactions of American Foundrymen""s Society, 1986, pages 403-416. While this experimental work studied these alloy systems, the investigations did not optimize the microstructure to provide tougher, more wear and corrosion resistant alloys.
One object of the present invention is to provide an improved process for making an iron-based casting alloy having improved combinations of toughness, abrasion resistance and corrosion resistance.
In carrying out the above object, the process of the invention for making the iron-based casting alloy is performed by precipitating eutectic chromium carbides of a first alloy system and primary carbides of a second alloy system including either vanadium carbides, niobium carbides, titanium carbides or combinations of these carbides. The primary carbides are precipitated at a primary carbide liquidus of the second alloy system which has a eutectic that is maintained below an austenite liquidus of the first alloy system to prevent formation of eutectic carbides of the second alloy system.
The eutectic chromium carbides of the first alloy system are precipitated at a eutectic thereof without forming primary chromium carbides.
Proeutectic austenite can be precipitated at an austenite liquidus of the first alloy system prior to the precipitation of the eutectic chromium carbides.
The objects, features, and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when considered with the accompanying drawings.